You will need to migrate to the same version of Confluence. So you can either download the same version as you currently have on your server or you can upgrade your current instance prior to migration.

See answers to your questions below:

- How does this work with our current licence? You will use the same licence key on both instances. After the migration is complete if both instances uses separate DBs, you can update the old instances license to a developers license so you can validate the migration.